1. Field of the Invention
The present invention relates to a breather system for a fuel tank capable of reliably functioning when a vehicle is inclined to the right or to the left, and a straddle-type four wheeled all terrain vehicle comprising the breather system.
2. Description of the Related Art
In general, a straddle-type four wheeled all terrain vehicle is a four-wheeled motorcycle called an xe2x80x9call terrain vehicle (ATV)xe2x80x9d. Since this type of vehicle is capable of stably traveling over sandy soil, rough terrain, and wet terrain and carrying a great deal of luggage and various equipment, it is utilized in various uses including leisure, sport activities, border patrols, etc.
The all terrain vehicle travels on the above-described terrains, and therefore, dust, water splash or the like is often generated during traveling. Also, the vehicle sometimes travels across puddles, streams, or the like. Since it is highly probable that the dust, water, or the like enters an air intake part having an intake port (ambient side opening) such as an air cleaner, it is desirable to provide the intake part at the highest possible position of the vehicle""s body.
In addition, in some all terrain vehicles on which a V-type engine is mounted, the air cleaner is placed above the engine, i.e., at a position at which the fuel tank has been conventionally placed, and for this reason the fuel tank is placed below a seat that a rider straddles and between two rear wheels.
In the constitution in which the fuel tank is placed above the engine, since fuel from the fuel tank is supplied to a carburetor by gravity, a pump for this supply is unnecessary. However, in the above-described constitution in which the fuel tank is placed below the seat, the fuel tank is inevitably located at a position substantially as high as or lower than the carburetor. Accordingly, in this constitution, there is a need for a fuel pump.
It is required that a fuel inlet of the fuel tank be located so as to be accessible from outside. In the constitution in which the fuel tank is located below the seat, the fuel inlet and a tank cap covering it are exposed from a rear fender by the side of the seat.
In the fuel tank, it is necessary to keep its internal pressure constant for the purpose of stably supplying the fuel to the engine through the carburetor. In a general vehicle, this can be easily achieved by providing a small opening in the tank cap. However, in case of the all terrain vehicle traveling on the above-described terrains, the fuel in the fuel tank might leak from the opening due to vibration during traveling, inclination of the vehicle body or the like.
Under these circumstances, the prevention of leakage of the fuel and the stable supply of ambient air into the fuel tank have been challenging tasks to the breather system of the fuel tank. By way of example, as disclosed in Japanese Patent No. 2795649, a breather hose is connected to the opening of the tank cap and an ambient-side opening of the breather hose end is fixed at a position of the vehicle body (e.g., handle) higher than the tank cap opening.
In the constitution in which the fuel tank is placed below the seat and the tank cap is provided on one of right and left sides of the seat, when the vehicle is inclined toward the tank cap side, the fuel runs into the corresponding breather hose, thereby causing the function of the breather to be unreliably performed.
The present invention addresses the above-described condition, and an object of the present invention is to provide a breather system for a fuel tank capable of functioning even if a straddle-type four wheeled all terrain vehicle in which a fuel tank is placed below the seat is inclined to the right or to the left, and a straddle-type four wheeled all terrain vehicle comprising the breather system.
To addresses the above-described conditions, according to the present invention, there is provided a breather system for a fuel tank comprising: a plurality of openings provided in the fuel tank; breather hoses respectively connected to the openings; a collecting pipe integrally connecting the breather hoses; and a check valve connected to an ambient side of the collecting pipe, wherein the plurality of openings are provided on opposite sides of the fuel tank so as to be spaced apart from each other.
According to the present invention, the plurality of breather openings are provided in the fuel tank and the breather hoses respectively connected to these openings are placed on the opposite sides of the fuel tank so as to be spaced apart from each other. Therefore, even if the vehicle is inclined to any of the opposite sides, the breather hose on the other side can be reliably operated.
In the present invention, the plurality of breather openings need to be spaced apart from each other but a distance between them or the like is not limited. It is desirable to place these openings in a space which is not occupied by the fuel in the fuel tank, that is, a space which contains air (basically at the highest position of the fuel tank) according to the degree of inclination of the fuel tank. Since there is sometimes provided an inflated space, for example, so-called air reservoir, depending on the shape of the fuel tank, it is advantageous in the present invention that the breather openings are placed at the air reservoir in which air is reserved substantially all the time regardless of such inclination.
It should be noted that the breather hose may be connected to a tank cap of the fuel tank.
Since the breather hoses respectively connected to the breather openings are integrally connected by means of the collecting pipe and the ambient side of the collecting pipe is connected to the check valve, the fuel tank having the plurality of openings can be embodied with a simple structure. The space in the fuel tank communicates with ambient via one or both of the breather hoses when the internal pressure of the fuel tank becomes positive or negative, thereby keeping the internal pressure of the fuel tank substantially constant.
Since the plurality of breather hoses are integrally connected and connected to the check valve, only one check valve is needed.
A catch tank having a predetermined space inside thereof may be interposed between the collecting pipe and the check valve and provided integrally with the check valve. In this case, even if the internal pressure of the fuel tank is increased to cause the fuel to be pushed out from the fuel tank through the breather hose, the fuel is temporarily stored in the catch tank without running to the outside. Moreover, the catch tank and the check valve can be compactly arranged together.
In this case, by positioning the catch tank to be higher than the fuel tank or the breather openings to which the breather hoses are connected, the fuel stored in the catch tank can be returned into the fuel tank by gravity when the internal pressure of the fuel tank is returned to normal.
Since the catch tank is directly connected to the check valve, a piping such as a connecting hose between them becomes unnecessary and the breather system can be simplified.
According to the present invention, there is also provided a straddle-type four wheeled all terrain vehicle, comprising: a vehicle body frame constituting the vehicle""s body; a straddle-type seat mounted to an upper portion of the frame; a fuel tank placed below the seat; and a breather system for the fuel tank, wherein the breather system includes: a plurality of breather openings provided in an upper portion of the fuel tank such that they are spaced apart from each other on right and left sides; breather hoses respectively connected to the breather openings; and a collecting pipe integrally connecting the breather hoses; and a check valve connected to an ambient side of the collecting pipe.
According to the present invention, the plurality of breather openings are provided in the fuel tank below the seat (in particular, in a space surrounded by the upper frames, the lower frames, and the rear upper frames, in case of the frame structure of the double-cradle type), and the breather hoses respectively connected to these openings are provided in the fuel tank such that they are spaced apart from each other on the right and left sides. Therefore, in the straddle-type four wheeled all terrain vehicle in which the fuel tank is placed below the seat and the fuel inlet is provided on one of right and left sides of the seat, even if the vehicle body is inclined to the right or to the left, the breather can be reliably functioned.
In this case, by providing the breather openings in a part of the fuel tank except the tank cap, the breather hoses connected to these openings can be easily placed inside of the rear fender not interfering with the rider.
In this case, since the breather hoses respectively connected to the breather openings are integrally connected by means of the collecting pipe (e.g., T-shape point) and the ambient-side of the collecting pipe is connected to the check valve, the fuel tank having the plurality of breather openings can be realized with a simple structure. When the internal pressure of the fuel tank becomes positive or negative, one or both of the breather hoses allow a space in the fuel tank to communicate with ambient, thereby keeping the internal pressure of the fuel tank substantially constant.
The ambient-side opening end of the check valve may communicate with a space in the pipe-shaped frame constituting the vehicle body so as to be opened in the ambient air. In general, the inside of the vehicle body frame is a clean room having a relatively large space closed by welding, which is suitable as an air intake passage. By making the ambient-side opening end of the check valve communicate with the space inside the frame, even if the fuel exceeding the capacity of the catch tank goes through the check valve, this fuel is stored in the frame without contaminating a road surface or the like. Needless to say, to open the space inside the frame with which the ambient-side opening end of the check valve communicate in the ambient air, the opening needs to be provided at any position of the frame.
An insertion portion with barb for preventing disengagement from the frame may be provided at the ambient-side opening end (in general, connected by a suitable breather hose) of the check valve which is connected to the frame.
It should be appreciated that the pipe-shaped frame need not be a frame relating to a structure of the vehicle body such as the body frame but may be a suitable frame provided in the vehicle. Preferably, the pipe-shaped frame is an upper frame that forms an upper portion of the body frame of a double-cradle type body frame and supports the seat. The frame is not limited to a pipe frame having a circular cross section but may be frames having cross sections of various shapes and a suitable space inside thereof.
In a case where the fuel inlet is provided on one of right and left sides of the fuel tank, the all terrain vehicle may be constituted as described below for the purpose of reliably functioning the breather when the vehicle is inclined to the right or to the left.
For example, the fuel inlet may be provided in a portion formed by upwardly extending part of the upper surface of the fuel tank such that an air reservoir is provided below the fuel inlet. A first breather opening may be formed in the air reservoir and connected to the first breather hose. A second breather opening may be formed in the upper face of the fuel tank on the opposite side of the first opening and connected to a second breather hose.
The check valve may be of various types. In order to prevent mixing of the fuel from the fuel tank with the ambient air, preferably, a check valve having two chambers, in which an air-intake side and a discharge side are independently formed for introducing the air between the inside of the tank and the ambient, is employed.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.